CAREER: Stratified Mixing in Sheared and Zero-Mean-Shear Turbulent Environments

职业：剪切和零平均剪切湍流环境中的分层混合

• 批准号: 2236654
• 负责人: Blair Johnson
• 金额: $ 50.07万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-01 至 2028-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2236654&HistoricalAwards=false
• 关键词: CAREER; Stratified; Mixing; Sheared; Zero

Mechanisms by which mass transport and mixing occur remain to be well-understood in flows for which there are interacting sources of energetic turbulence. The primary aim of this project is to evaluate various types of mass transport that occur from the interaction between mean shear stress (i.e. generated by velocity gradients in unidirectional flow) and instantaneous and localized shear stress generated by chaotic turbulence in the presence of density stratification. Findings from this work will improve understanding of deep ocean mixing, brine discharges in bays or subglacial lakes, saltwater intrusions in rivers, and avalanches, among others. The work will include mentorship of a graduate student and undergraduate researchers through the Graduates Linked with Undergraduates in Engineering program that supports women in STEM. The PI will develop large-scale public engagement events surrounding environmental mixing processes through art exhibits and educational modules. Further, the research team will partner with a local science museum to develop a permanent exhibit as well as a hands-on laboratory workshop for K-12 home-schooled students to study gravity currents; data generated from these experiments will be shared with the research community. The overarching goal of this research is to comprehensively evaluate the independent and combined roles of energetic turbulent flows with and without current-generated shear acting upon density-stratified fluid systems. This will be achieved via a comprehensive laboratory approach using unique and highly controllable facilities that allow full quantification of links between flow energetics, buoyancy, and fluid properties with mixing and mass transport dynamics. Three distinct flow scenarios will be considered: turbulence with no mean current, a density current released into fluid with background turbulence, and advection of turbulence over a density interface. Non-invasive quantitative imaging techniques will be used to measure velocity and mass concentration fields to characterize flow dynamics. This systematic approach will provide an understanding of how competing sources of turbulence contribute to mixing and transport, particularly when shear-driven flows act in conjunction with background turbulence. Impacts are expected to be far-reaching, with direct and practical means for implementing the scientific knowledge gained through the laboratory and synthesis efforts. Additionally, significant outcomes are expected via the complementary educational and public outreach activities designed to engage women and home-schooled K-12 students, along with the general public. These activities will be assessed annually throughout the duration of the proposal period to foster continued improvement of equity, diversity, and inclusivity in STEM.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在存在相互作用的能量湍流源的流动中，发生质量传输和混合的机制仍有待于很好地了解。这个项目的主要目的是评估在密度分层存在的情况下，平均剪应力(即由单向流动中的速度梯度产生的)与由混沌湍流产生的瞬时和局部剪应力之间相互作用所产生的各种类型的质量传输。这项工作的发现将提高对深海混合、海湾或冰下湖泊卤水排放、河流咸水入侵和雪崩等问题的理解。这项工作将包括指导一名研究生和本科生研究人员，通过与支持STEM女性的工程本科生计划相联系的毕业生。国际和平协会将通过艺术展览和教育模块，围绕环境混合过程开展大规模的公共参与活动。此外，研究小组将与当地一家科学博物馆合作，为K-12家庭教育的学生开发一个永久性展览和一个动手实验室研讨会，以研究重力流；这些实验产生的数据将与研究界共享。这项研究的首要目标是全面评估有和没有水流产生的切变作用于密度分层流体系统的高能湍流的独立和联合作用。这将通过使用独特且高度可控的设施的综合实验室方法来实现，这些设施允许完全量化流动能量学、浮力和流体特性与混合和质量传输动力学之间的联系。将考虑三种不同的流动场景：没有平均流的湍流，释放到有背景湍流的流体中的密度流，以及密度界面上的湍流平流。非侵入式定量成像技术将被用来测量速度场和质量浓度场，以表征流动动力学。这一系统的方法将有助于理解相互竞争的湍流源如何促进混合和输送，特别是当剪切驱动的流动与背景湍流一起作用时。预计影响将是深远的，有直接和实际的手段来落实通过实验室和综合努力获得的科学知识。此外，通过旨在吸引妇女和接受家庭教育的K-12学生以及普通公众参与的补充教育和公共宣传活动，预计将取得重大成果。这些活动将在整个建议书期间每年进行评估，以促进STEM的公平性、多样性和包容性的持续改善。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。